The present invention relates to an improved fluid filter, and more particularly to a fluid filter which is particularly adapted to filter particulate matter from liquids such as in the effluent from wastewater treatment facilities such as septic tanks.
Devices for filtering particulate matter from liquids, and even those specifically directed to the removal of effluent from wastewater treatment facilities such as septic tanks, are well known. However, although the prior art is highly developed, certain deficiencies in this general area exist.
U.S. Pat. Nos. 2,900,084, 3,332,552, 4,439,323 and 4,179,372 all disclose filters for the removal of solid matter from fluids, particularly for treatment of sewage in septic tanks and for removal of other solid matter from liquids. While some of these prior art devices have proven effective, they are expensive to produce and have resulted in mechanical and other problems associated with the plugging and cleaning.
More recent U.S. Pat. No. 5,382,357 has stated as its objective to remedy the problems associated with the above-mentioned prior art devices. This reference discloses a filter device which includes a tubular filter element (11,13) with a series of slots (12,14) of selected width extending through the tubular element (11,13). The element (11,13) has a central opening (7,8) and can be received in a casing (3) to form an annular area (16) between the tubular filter element (11,13) and the casing (3) so the central opening (7,8) is open to receive the fluid to be filtered as the fluid flows through the slots (12,14) from the central opening (7,8) to the annular area (16). The casing (3) can also include an outlet (2) from the annular area (16) so the fluid can be emitted from the assembly. A seal (24) can be provided between the tubular element (11,13) and the inside of the casing (3) at a location below the slots (12,14) in the tubular element (11,13) and above the outlet (2) from the casing (3).
While this filter may have remedied some of the problems associated with the earlier prior art, it suffers from a number of disadvantages of its own. One of such disadvantages is that it is only useful for filtering relatively large particles. While the size of slots (12,14) may be varied, if they are made small enough to filter out smaller particles, they will be prone to being quickly clogged by larger particles, as the filter is only a single-pass filter. That is, fluid flows up through the interior of the filter and then only once through any type of a filter element.
A related problem is that even if the slots (12,14) are properly sized to filter out the desired particles, the filter is still prone to clogging. This is true because the surface area of the filter is limited by the length of the casing (3). More specifically, for the filter to function properly, there must be a seal (24) between the tubular element (11,13) and the inside of the casing (3) at a location below the slots (12,14).
If there were no seal, fluid could flow unfiltered up through annular area (16) and out through outlet (2). Thus, if casing (3) is short, the filter will necessarily have to be short, and the surface area of the filter (i.e., the area covered by slots) will be small and prone to rapid clogging.
What is desired, therefore, is a filter for filtering particulate matter from liquids which is inexpensive to produce, which is useful for filtering small as well as large particles, which is not prone to rapid clogging, and which is not limited in size by the length of the casing in which it is inserted.
Accordingly, it is an object of the present invention to provide a filter for filtering particulate matter from liquids which is inexpensive to produce.
Another object of the present invention is to provide a filter for filtering particulate matter from liquids having the above characteristics and which is useful for filtering small as well as large particles.
A further object of the present invention is to provide a filter for filtering particulate matter from liquids having the above characteristics and which is not prone to rapid clogging.
Still another object of the present invention is to provide a filter for filtering particulate matter from liquids having the above characteristics and which is not limited in size by the length of the casing in which it is inserted.
These and other objects of the present invention are achieved by provision of a filter for filtering particulate matter from liquids adapted to be received in a filter casing having a casing wall and an outlet. The filter includes a filter element having a plurality of openings therein for filtering particulate matter while allowing liquids to pass therethrough, the filter element comprising a first section located proximate to the outlet in the casing and a second section adjacent to the first section. The filter element is receivable in the casing and spaced apart from the casing wall such that the filter element and the casing wall define a space therebetween. A seal separates the first section and the second section of the filter element and prevents the flow of liquid therearound in the space between the filter element and the casing wall. The seal is located below the outlet in the casing. A lower end member closes a lower end of the filter element, the lower end member preventing the flow of unfiltered liquid and particulate matter into the filter element. Thus, fluid is forced to flow from outside the filter element to inside the filter element through the second section, thereby filtering the fluid a first time, and then from inside the filter element to outside the filter element and out through the outlet through the first section, thereby filtering the fluid a second time.
The lower end member may comprise a filter material having a plurality of openings therein, or may comprise a solid member having no openings therein, so long as the lower end member prevents the flow of unfiltered liquid and particulate matter into the filter element. The filter element may comprise a rigid material having a plurality of openings therein, or may comprise a flexible mesh or screen material having a plurality of openings therein.
Preferably, the filter also includes a rigid insertion member and an upper end member attached to an upper end of the filter element, the upper end member having a hole therein adapted to receive the insertion member therein. When such is the case, the lower end member preferably has a recess therein adapted to receive the insertion member such that the insertion member exerts a force on the lower member as the filter is being inserted into the casing. Such is most desirable when the filter element comprises a flexible mesh or screen material so that the insertion member inhibits the filter element from collapsing. Most preferably, the insertion member is removable from the filter element, and the lower end member includes a taper surrounding the recess therein for facilitating insertion of the insertion member into the recess therein. When the insertion member is removable from the filter element, it is also most preferable that the upper end member and the insertion member include a means for detachably connecting the insertion member to the filter element.
When an upper end member is attached to an upper end of the filter element, is also preferable that the upper end member have a seal preventing the flow of liquid therearound in the space between the filter element and the casing wall, the seal being located above the outlet in the casing. Such is preferable so that liquid flowing out through the first section of the filter element is forced to flow through the outlet in the casing.
Also preferable is if the lower end member comprises a plurality of centering elements extending radially outwardly therefrom which are sized, shaped and positioned to engage an inner surface of the casing wall such that the filter element is centered within the casing, while still allowing liquid to flow therearound. Moreover, the filter preferably also includes at least one strengthening ring peripherally attached to the filter element to provide strength and rigidity thereto. The strengthening ring may comprise a plurality of centering elements extending radially outwardly therefrom similar to the centering elements of the lower end member.
Most preferable is if the plurality of openings in the first section of the filter element are smaller than the plurality of openings in the second section of the filter element, such that larger particles of matter are first filtered out by the second section during a first pass of the liquid through the filter element before smaller particles of matter are filtered out by the first section during a second pass of the liquid through the filter element. When such is the case, the larger particles in the liquid cannot prematurely clog the smaller openings of the first section, as they are filtered out during the first pass through the filter. Also most preferable is if the second section of the filter element extends out beyond a lower end of the casing.
The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.